This invention relates to scroll compressors, and in particular to a multi-stage scroll compressor having more than one discharge pressure, and which can operate as a compressor or as a vacuum pump.
Many pneumatic applications require combinations of discharge pressures. Such combinations include, for example, pressure and vacuum, pressures at two or more discharge pressures, and higher pressures requiring two or more stages. Applications where such combinations are currently required include pneumatic controls for heart balloons which require pressure and vacuum, and refrigerant recovery systems which require high pressures for the recovery of refrigerant and a vacuum for evacuating the refrigerant system before charging of the system. In systems which require high pressures, such as refrigerant recovery systems, it is generally beneficial to have a two stage compressor and a vacuum pump.
It is presently common to separate the compressor and vacuum functions. For example, a separate compressor and vacuum pump are used in refrigerant recovery. One is used to recover the refrigerant and another unit is used to evacuate the system. The pneumatic controls for heart balloons include a compressor mounted to one end of the motor and a vacuum pump mounted to the opposite end. The compressor will then fill the balloon and the compressor will deflate the balloon. In multi-stage applications, more than one pumping unit is typically employed.
The use of two units adds cost and complexity to devices, such as those noted above. It would be beneficial if the two functions could be incorporated into a single device.